holley carb electric choke wiring

ok, so I am looking to wire my electric choke on the holley carb. so far I just ran a short jumper ground from the ground terminal to under a screw that holds the choke assembly to the body of the carb as it shows in the holley website. Now I am looking to run a positive 12v wire to feed this. It says it should only be working when the key is in the on position or the car is running? Where would the best place be to do this? Am I missing smoething here? I have the yellow and brown wires going to my starter relay. The brown is the tranny neutral safety switch. The yellow I believe goes to the ignition key. Can I tap into one of these wires? How can I test them to be sure they are working and have keyed power?